Under Armour was founded in 1996 by Kevin Plank, a then 23-year old former special teams captain of the University of Maryland football team. Plank initially began the business from his grandmother's basement in Washington, D.C.[6] He spent his time traveling up and down the East Coast with nothing but apparel in the trunk of his car. His first team sale came at the end of 1996 with a $17,000 sale. From his grandmother's basement, Plank moved to Baltimore, Maryland. After a few moves in the city he landed at his current headquarters in Tide Point.[6]

As a fullback at the University of Maryland, Kevin Plank got tired of having to change out of the sweat-soaked T-shirts worn under his jersey; however, he noticed that his compression shorts worn during practice stayed dry. This inspired him to make a T-shirt using moisture-wicking synthetic fabric.[7] After graduating from the University of Maryland, Kevin Plank developed his first prototype of the shirt, which he gave to his Maryland teammates and friends who had gone on to play in the NFL. Plank soon perfected the design creating a new T-shirt built from microfibers that wicked moisture and kept athletes cool, dry, and light.[6] Major competing brands including Nike, Adidas and Reebok would soon follow in Plank's footsteps with their own version of Under Armour's moisture-wicking apparel.[8] Plank opted to use the British spelling "armour" in the company name because the Internet domain name was still available for that version.[9]

People began to take notice of the brand when a front page photo of USA Today featured Oakland Raiders quarterback Jeff George wearing an Under Armour mock turtleneck. Following that front page, Under Armour's first major sale came, when an equipment manager from Georgia Tech requested 10 shirts from Plank. This deal opened the door to a contract with Arizona State University, North Carolina State and other Division I football teams. With positive reviews from players, word began to spread and orders began to increase.[7] That same year, Under Armour launched with several new apparel lines including ColdGear, TurfGear, AllseasonGear, and StreetGear.[7] By the end of 1996, Under Armour had sold 500 Under Armour HeatGear shirts, generating $17,000.[7] In 1997, Plank had $100,000 in orders to fill and found a factory in Ohio to make the shirts.

Part of the Under Armour Headquarters located in Locust Point, Maryland

The following year, Under Armour became the outfitter of the new XFL football league, gaining even more attention during the league's debut on national television.[7] In 2003, the company launched its first television commercial, which centered on their motto, "Protect this house."[6] In late 2007, Under Armour opened its first full-line full-price retail location at the Westfield Annapolis mall in Annapolis, Maryland.[10]

It has also opened several specialty stores and factory outlet locations in Canada, China, and 39 states including the opening of its first Brand House in Baltimore in 2013 and second Brand House in Tyson's Corner, VA.[11]

Under Armour has also opened the Brand's first store outside of North America, which is located in Edinburgh, Scotland and is run and owned by First XV, the rugby store situated next door. In 2009, baseball Hall of Famer Cal Ripken Jr. formed an alliance under which the company would have significant presence at several venues and events under the auspices of Ripken Baseball, including providing uniforms for the minor league Aberdeen IronBirds and youth teams participating in the Cal Ripken World Series.[12]

The company is reported to be the major commercial sponsor for the reality TV show Duck Dynasty, and has garnered attention for taking a stand supporting show "patriarch" Phil Robertson.[13]

Under Armour provided the suits worn by speedskaters in the 2014 Winter Olympics. The U.S. speedskaters were losing while wearing the new Mach 39 speedsuits, but when they reverted to the previous model suits, the skaters continued to lose. Although there did not appear to be a design flaw in the suit that caused the poor results, the news of the suits caused Under Armour stock to drop 2.38%.[14]

The company, offering a reported US$250 million over 10 years, also bid hard over Nike Lathe to sign NBA MVP Kevin Durant to an endorsement deal. However, Nike ultimately re-signed Durant after agreeing to structure a contract, offering US$300 million.[15]

On January 21, 2014, it was announced that the University of Notre Dame and Under Armour had come to terms on providing uniforms and athletic equipment for the university. This 10 year deal is the largest of its kind in the history of college athletics and is effective July 1, 2014. As of 2014, Under Armour has operated revenue and operating profit more than 30%, accelerating from their 2013 pace. Its share price has soared 62.5% this year.[15]

After its November 2013 acquisition of digital app maker MapMyFitness for US$150 million, in February 2015 Under Armour announced it had purchased the calorie and nutrition counting app maker MyFitnessPal for $475M, as well as the fitness app maker Endomondo for US$$85 million.[16][17]

The expansion of Under Armour's product lines, such asTurfGear, AllseasonGear, and StreetGear put Under Armour at the forefront of the emerging performance apparel industry.[6] In 2003, Under Armour launched their Women's Performance Gear product line.[6]

Under Armour announced an addition to their ColdGear product line, called Infrared, that was released in 2013.[18] This line claims to disseminate heat using ceramic powder and re-circulate heat around the wearer’s body. This was purportedly designed so that the wearer's heat signature will not be picked up. Under Armour also had released a product with scent control technology in 2012 titled, "Under Armour Scent Control". This line claims to be designed so that the wearer's scent cannot be detected.[19]

Under Armour outlet store in Henry County, Georgia

Under Armour is inventing a new type of shirt called "Coldblack," which is designed to reflect heat and keep athletes cool in the sun.[20] Under Armour has come out with new styles for football uniforms. In October 2012, Under Armour created "The Wounded Warrior" project for football uniforms.[21] The University of Hawaii and Boston College wore the star studded cleats and the American striped jerseys. They were revealed when Boston College played Maryland on October 27, 2012, also when Hawaii played UNLV on November 24, 2012.[21]

The company produces the Speedform shoe in a Chinese bra factory. It has no insole and little stitching. Shoes are Under Armour's fastest growing product line, growing 31% from 2011 to $239 million in sales in 2012.[22]

On April 29, 2009, the United States Consumer Products Safety Commission announced a voluntary recall of all Under Armour brand athletic cups. The cups might break when hit, posing a risk of serious injury. They were sold from January 2006 through March 2009.[23]

On November 3, 2011, the United States Consumer Products Safety Commission announced a voluntary recall of all Under Armour Defender chin straps. The straps pose a laceration hazard when a player contacts the metal snap. They were sold from January 2008 through September 2011.[24]

UA Give Back is Under Armour's effort to become involved in different facets of the world community. They have different branches in their organization that specialize in each cause that Under Armour supports. They consist of the UA Power in Pink, UA Freedom and UA Win Global.[25]

UA Power in Pink is an Under Armour program that promotes women using exercise and fitness to fight breast cancer.[26]UA Freedom is an Under Armour program that supports the efforts of the Wounded Warrior Project whose mission is to honor, raise awareness, and aid wounded veterans and military service members.[27]UA Win Global is a children's athletics program which focuses on "underserved communities" by enhancing play areas, investing in sports programs and providing support for sports coaches.[28]

As of 2012, Under Armour was the sponsor of the Baseball Factory's "Premium Video Program", which holds more than 100 events for youth athletes across the United States annually.[29]

Under Armour took over as the main uniform and equipment provider of the University of Maryland in College Park, Maryland. Founder Kevin Plank graduated from the school in 1996. They provide every athletic team at the university with uniforms and other products as well, similar to the relationship Nike has with the University of Oregon where Phil Knight graduated. They have unveiled numerous new uniforms and combinations for every men's and women's team at the school. Under Armour and Kevin Plank have sponsored many of the schools teams, facilities, and former athletes since Plank founded the company in 1996.

Any Given Sunday – Signed on to provide their apparel to Oliver Stone's film. The key scenes that featured Under Armour gave the products relevancy in the sporting nation. This product placement led Kevin Plank to place an ad in ESPN the Magazine to capitalize on the national exposure.[6]

The Challenge (Seasons 15–present) – Under Armour have provided the contestant's jerseys for them to wear when they are in competition.[122]

^Salter, Chuck (August 2005). "Protect This House". Fast Co.Retrieved May 2, 2015 – via FastCompany.com. Plank may have caught the megabrands snoozing, but now they're wide awake, and his company is under siege from Nike Dri-Fit, Adidas ClimaLite, Reebok Hydromove, and others